This invention concerns a method to obtain a plurality of sections and/or bars (long products) in the cold state at one and the same time; the invention concerns also the sections and/or bars thus obtained.
The method consists in obtaining from a hot rolled product a multiple-section element including a finished plurality of sections and/or bars, in cooling this multiple profile in a production line and in arranging to split the various sections and/or bars in the cold state at one and the same time without interrupting continuous production.
To be more exact, this invention concerns a method for obtaining simultaneously in the cold state a plurality of sections and/or bars of long products from one single multiple-section element having a special multiple profile produced in a hot rolling mill, with the plurality of sections or bars joined together lengthwise by webs.
Nowadays, the hot rolling mills to obtain long products in particular, and not only those which serve to obtain sections, are sized on the basis of the hourly capacity of the heating furnaces, the power of the drive motors, the rolling mill stands, the transmission means and the lubrication and cooling services; moreover, they have to take account of the desired output and the rolling stresses generated by the thicker sections.
It follows that, when a given rolling mill is producing smaller sections or the smallest sections, the conversion costs increase appreciably because the plant is not employed correctly with the technology of the state of the art.
For this reason rolling plants are dimensioned in relation to a limited dimensional range of products so that the rolling mill will provide an acceptable average efficiency in relation to the sizes processed.
The plants therefore are designed, in fact, specially and are classified according to the four dimensional categories of sections and/or bars; these dimensional categories are defined as small, medium, heavy and extra-heavy sections and/or bars.
This means that, to cover a broad slice of the market in a reasonable and adequate manner, a producer is compelled to have a plurality of hot rolling plants so as to be able to produce economically more than one dimensional category of sections and/or bars.
A producer who has one given rolling plant will have to be content with producing only that specific dimensional category of sections and/or bars.
The state of the art includes the hot rolling of two or more small sections at the same time; these small sections are hot rolled at the same time while forming one single element which comprises these sections joined together lengthwise.
Immediately after the hot rolling these small sections are split from each other lengthwise in the hot state in the rolling mill itself.
These small sections and/or bars thus split in the hot state create great handling problems because they cannot be controlled adequately in the three-dimensional positioning they take up. These problems occur mainly in the braking services, in the cooling, in the measuring, in the separation, in the preparation of layers of the sections and/or bars, in the feed to the straightening process and generally in all the other processes downstream of the hot rolling and splitting.
The reason for this is that the automatic handling of a plurality of bars and/or sections in the hot state arriving at the same time in the services downstream of the hot rolling and splitting leads to piling up, twisting, uneven cooling, misalignments, bending, etc.
This entails severe problems as regards production, design, construction, use and running and also safety. The state of the art requires also a great number of persons employed in the services downstream of the hot rolling and splitting since the automation of the operations of finishing, packaging and possible quality control in-line in the plant manufacturing long finished products becomes complex, complicated and not always capable of being resolved satisfactorily.